1. Field of the Invention
The present invention relates to a method for treating a virus infection, comprising administering to a subject in need a derivative of aniline. In particular, the method of the present invention is effective in inhibiting virus-induced apoptosis, inhibiting virus-induced cytopathic effect, and/or inhibiting viral replication in a virus-infected cell. The method of the present invention may further comprise administering to the subject an interferon to provide a synergistic effect in treating a virus infection.
2. Descriptions of the Related Art
A virus is non-cellular and consists of genetic materials (DNA or RNA) and protein coats (some viruses can form an envelope of lipids that surrounds the protein coat when they reach the surface of host cells). A virus is a segment of DNA or RNA coated by a protective coat. A virus cannot reproduce by itself due to its simple composition. Virus replication is conducted by using the system of a host cell through an infection mechanism to synthesize and assemble various viral proteins and viral nucleic acids. The replication cycle of a virus through a virus-infected cell can be classified into approximately six steps as follows: attachment, invasion, uncoating, synthesis, packaging and release.
It has been known that the gene structure and replication cycle of viruses in the same genus are very similar. For example, the genome of Flavivirus genus virus is a positive single strand RNA. The complete genome is about 11 kilobases (kb) in length. There is high conservation between gene sequences in the genome. For example, the 5′-end of the genomic RNA has a Type I cap, the 3′-end of the genomic RNA lacks a poly A tail, and each of the 5′ and 3′ ends of the genomic RNA has an untranslated region (UTR), which can form a highly conserved secondary structure. There is a big open reading frame (ORF) between these two UTRs. The ORF can be translated into a polypepetide which can sequentially generate three structural proteins (i.e., core protein, pre-membrane protein, envelope protein) and seven non-structural proteins, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5. The viral particles of the Flavivirus genus virus can bind to the receptors on a host cell by its envelope proteins to enter the host cell through a receptor-mediated endocytosis, and then change the structure of the envelope proteins by an endosome acidification to conduct a membrane fusion with the endosome of the host cell, thereby releasing viral RNA genome into the cytosol of the host cell. The protein translation of the viral genome will then be directly conducted in the host cells to generate a long chain polyprotein which will be cleaved by signalases in the endoplasmic reticulum (ER) and viral NS2BNS3 protease, thereby generating the aforementioned three structural proteins and seven non-structural proteins. The viral genome is replicated and assembled with the viral proteins that have gathered in the ER to from a viral particle. The viral particle is then transported into the Golgi body and released from the virus-infected cell through exocytosis.
The Enterovirus genus virus is a positive single strand RNA. The complete genome is about 7.4 kb in length. There is high conservation between gene sequences in the genome. For example, VPg-5′-NCR, VP0 (VP4, VP2), VP3, VP1, VP2A, VP2B, VP2C, VP3A, VP3B, VP3C, VP3D and a poly A tail connected to 3′-end are presented sequentially, from the 5′-end to the 3′-end of the genomic RNA. VP0 is a precursor of VP4 and VP2 before separation. VP1, VP2, VP3 and VP4 are structural proteins of enterovirus, which relates to the characteristics of the virus infection in a host cell. Among these structural proteins, VP1, VP2 and VP3 are the primary proteins for composing a viral capsid, and VP1 also relates to the binding of cell receptors. When the viral particles of Enterovirus genus virus can bind to the receptors on the surface of a host cell, the N-terminal of viral protein VP1 will change structurally. VP1 will shift from the inside to the outside of the virion and form a channel with the receptors of host cells, thereby leading the viral genomic RNA to enter into a host cell. Then, the viral genomic RNA will be translated into multi proteins and cleaved by viral proteins such as VP2A, VP3C and VP3CD, to generate a viral outer sheath protein and a RNA polymerase, to accomplish the replication of the viral genomic RNA and form a new viral particle with infectious ability.
It has been known that some viruses in the Flavivirus genus, such as tick-borne encephalitis virus (TBEV), West Nile virus (WNV), yellow fever virus (YFV), Japanese encephalitis virus (JEV), and dengue virus (DEN) cause serious human diseases. The diseases caused by Japanese encephalitis virus or dengue virus are the most severe. Japanese encephalitis virus is transmitted through mosquito bites. Japanese encephalitis virus infection will cause acute cerebral meningitis (also referred to as “Japanese encephalitis”), leading to damage to the brain, spinal cord and meninges. The transmission of Japanese encephalitis virus usually occurs in summer and it is endemic in Southeast Asia, including Siberia, India, China, Taiwan, Japan, Korea, Philippine, Thailand. There are about 30,000 to 50,000 confirmed cases annually. The transmission of Japanese encephalitis virus in Taiwan occurs annually between May and October, and it usually peaks in July. The death rate ranges from 30% to 70%, especially when the severe state is reached, such as aseptic meningitis and respiratory failure. The death rate is especially high among children under 6 years of age and persons with a weak immune system over 65 years of age. A full-scale vaccination is only available in Taiwan, Japan, Korea, Thailand and Singapore. There are no specific drugs that can be used for treatment to date. In addition to supportive therapies, the only treatment that is used in clinics is a combination of an anti-virus drug, Ribavirin, and interferon. However, the prognosis is poor, and such treatment usually results in severe sequelae.
Dengue virus can be classified into four antigenically distinct serotypes: Type 1, Type 2, Type 3 and Type 4. Patients infected with dengue virus show symptoms such as sudden onset of high fever (≧38° C.), headache, retro-orbital pain, muscle pain, joint pain, and exanthema, which is referred to as “typical dengue fever.” Moreover, when being infected with different types of dengue virus, it has a higher probability of becoming “dengue hemorrhagic fever.” In addition to the aforementioned symptoms of typical dengue fever, dengue hemorrhagic fever can cause hemorrhaging. The incidence rate is especially high among children under 15 years of age. If not treated immediately, hyper-plasma leakage that is caused by severe hemorrhage may lead to shock or death. The death rate can be up to 50%. Dengue fever usually occurs in warmer seasons (i.e., May to October), and it is endemic in all areas of the world with subtropical climates (i.e., areas between northern latitude of 25 degrees and southern latitude of 25 degrees), including 61 countries. About 1.5 billion people live in a risk of dengue transmission. Between 1970 and 1980, there were about 250,000 infections of dengue hemorrhagic fever yearly. Dengue fever has been transmitted worldwide since the 1980's. There is no vaccine that can be used to date, and the only treatment is supportive therapy but not specific drugs.
The Enterovirus genus virus includes 23 types of group A coxsackievirus (CVA), 6 types of group B coxsackievirus (CVB), 3 types of poliovirus, 30 types of echovirus, and enterovirus types 68 to 71 (EV68 to EV71). The Enterovirus mainly infects children under 3 years of age, and is usually transmitted in the summer and fall. Persons infected with the enterovirus may have minor symptoms like a common cold, such as hand-foot-mouth disease and herpangina. Sometimes, an enterovirus infection may lead to special clinical manifestations, such as aseptic meningitis, viral encephalitis, myocarditis, paralysis syndrome, and acute hemorrhagic conjunctivitis. Since 1990, infectious cases have occurred in Taiwan, Hong Kong, China, Japan, Malaysia, Singapore and Macao. The cases of enterovirus infection are found all year round in Taiwan. Peak season is between April and September. In 1998, there was a largest outbreak of 130,000 cases of hand-foot-mouth disease and herpangina caused by EV71 and coxsackievirus A16 (CAV16). Most of the cases were reported between May and July and between September and November, including 400 cases with severe syndrome and 78 cases of death. There are no specific drugs to treat an enterovirus infection, especially EV71. Only supportive therapy can be used depending on the symptoms. There is one vaccine that is being developed in Taiwan, but it is still in phase II of the clinical trial, which is at least 4 to 5 years from clinical use. Furthermore, because there are over 100 types of enterovirus, it is unknown whether a single vaccine can be used to treat several kinds of enterovirus. In addition, some pharmaceutical companies now are in the process of investigating the drugs which can inhibit enterovirus. However, all of these drugs are still in undergoing clinical trials and thus, the safety in children cannot be thoroughly evaluated.
There is still a necessity and urgency for developing a drug for effectively treating a virus infection because supportive therapy is not sufficient
The inventors of the present invention found that the compound of formula (I) of the present invention can effectively inhibit virus-induced apoptosis, inhibit virus-induced cytopathic effect, and inhibit virus replication in a virus-infected cell. Furthermore, the compound of formula (I) can be used in combination with an interferon simultaneously or sequentially to generate a synergistic effect on treating a virus infection. In particular, the compound of formula (I) of the present invention can generate the aforementioned effects on Flavivirus genus virus and Enterovirus genus virus, especially on Japanese encephalitis virus, dengue virus and/or enterovirus type 71.